Extracorporeal blood treatment involves removing blood from a patient, treating the blood externally to the patient, and returning the treated blood to the patient. Extracorporeal blood treatment is typically used to extract undesirable matter or molecules from the patient's blood and/or add desirable matter or molecules to the blood. Extracorporeal blood treatment is used with patients unable to effectively remove matter from their blood, such as when a patient has suffered temporary or permanent kidney failure. These patients and other patients may undergo extracorporeal blood treatment to add or remove matter to their blood to maintain an acid/base balance or to remove excess body fluids, for example.
Extracorporeal blood treatment is typically accomplished by removing the blood from the patient in a continuous flow, introducing the blood into a primary chamber of a filtration unit where the blood is allowed to flow past a semipermeable membrane. The semipermeable membrane selectively allows matter in the blood to cross the membrane from the primary chamber into a secondary chamber and also selectively allows matter in the secondary chamber to cross the membrane into the blood in the primary chamber, depending on the type of treatment.
A number of different types of extracorporeal blood treatments may be performed. In ultrafiltration (UF) treatment, undesirable matter is removed from the blood by convection across the membrane into the secondary chamber. In a hemofiltration (HF) treatment, the blood flows past the semipermeable membrane as in UF and desirable matter is added to the blood, typically by dispensing a fluid into the treated blood either before or after it passes through the filtration unit and before it is returned to the patient. In a hemodialysis (HD) treatment, a secondary fluid containing desirable matter is introduced into the secondary chamber of the filtration unit. Undesirable matter from the blood crosses the semipermeable membrane into the secondary fluid and desirable matter from the secondary fluid may cross the membrane into the blood. In a hemodiafiltration (HDF) treatment, blood and secondary fluid exchange matter as in HD, and, in addition, matter is added to the blood, typically by dispensing a fluid into the treated blood before its return to the patient as in HF. To perform one of these extracorporeal blood treatments, blood must be continuously removed from either a vein or artery of the patient.
Traditionally each type of extracorporeal blood treatment has been conducted with a separate system because of the unique combination of fluids, flow rates, pressures and other parameters associated with each of the treatments. So, for example, manual systems used to perform HD on arterial blood rely on the arterial blood pressure to cause blood to flow past the membrane and be treated. Because a natural flow cannot be achieved when using venous blood, these systems cannot perform HD on venous blood and a separate machine or pump is required to establish a blood flow from a venous blood source and cause the venous blood to pass through the filtration unit and return the treated blood to a venous return point.
Traditionally, setup, monitoring and adjusting of each separate system or machine has been labor intensive. Setup, which includes assembling and priming of the extracorporeal blood treatment apparatus, can be especially time consuming. These manual systems are further labor intensive because of the need for personnel often to monitor continuously and to adjust fluid flow rates based upon visual observation. For example, during operation of some extracorporeal blood treatment machines, operators can only adjust the rate of removal of body fluid from the secondary chamber by raising or lowering the height of a container collecting the matter from the secondary chamber. Changing the height of the collection container effectively modifies the pressure across the semipermeable membrane, increasing or decreasing the rate at which body fluid passes from the blood across the membrane. To maintain the rates, the height of the collection container requires continual monitoring so that required adjustments may be made.
The connection of some manual extracorporeal treatment systems to patients can also be labor intensive, with connection to an artery of the patient particularly problematical. An arterial catheter connection must be constantly monitored, as it is susceptible to disconnection and any such disconnection can result in significant blood loss.
Previous extracorporeal blood treatment systems frequently require an operator to constantly monitor the treatment to detect operational conditions placing the patient at risk. Such conditions include leaking of blood at connection points of the blood flow lines to and from the extracorporeal blood treatment machine, clotting of blood in the semipermeable membrane, depletion of fluids in the containers of matter required for treatment, filling of the containers collecting matter during treatment, and existence of dangerously high or low pressures of blood or fluids during the treatment.
It is against this background that the significant improvements and advancements of the present invention have taken place in the field of extracorporeal treatment of blood.